Metabolites of All-trans-Retinol in Day 10 Conceptuses of Vitamin A-Deficient Rats

It has been previously demonstrated that vitamin A-deficient rats supplemented with retinoic acid cannot complete gestation. Resorption of fetuses invariably occurs in these animals beginning Day 15 of gestation. Retinol must be administered on or before Day 10 of gestation in order to prevent this phenomenon. The administration of as little as 2 μg on Day 10 is sufficient to allow continuation of gestation through parturition. This study examines the metabolites of all-trans-retinol in the conceptuses of vitamin A-deficient, retinoic acid-supported pregnant animals at Day 10 of gestation. The retinoids recovered in this study could be identified as all-trans-retinol, retinyl palmitate, and other retinyl esters. Virtually no radiolabeled retinoic acid was found in the conceptuses of these animals over the 12-h period examined. This may suggest that retinoic acid that may be required by the fetus can arise directly from maternal sources. Additionally, the isolation of an early appearing, very polar metabolite of retinol is reported. This aqueous-soluble compound accounts for more than 20% of the radioactivity recovered at 1 h post-dose. The amount of this compound increases through 6 h post-dose. This metabolite is not found in urine from the same animals and is not likely to be an excretion product.